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https://issues.apache.org/jira/browse/CASSANDRA-15241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17043365#comment-17043365
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Benedict Elliott Smith edited comment on CASSANDRA-15241 at 2/24/20 10:21 AM:
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It's worth noting that running time accuracy depends on the compiler emitting
the right instructions, which it's under no duty to do with the JMM (this was
true before too). This is probably fine, since it's likely to and this doesn't
impact system correctness, but we could also utilise either {{volatile}} or
{{volatile}} with {{lazySet}} when setting the {{approxTimeOfStart}} value in
each {{DebuggableTask}} to guarantee it.
was (Author: benedict):
It's worth noting that running time accuracy depends on the compiler emitting
the right instructions, which it's under no duty to do with the JMM (this was
true before too). This is probably fine, since it's likely to, but we could
also utilise either {{volatile}} or {{volatile}} with {{lazySet}} when setting
the {{approxTimeOfStart}} value in each {{DebuggableTask}} to guarantee it.
> Virtual table to expose current running queries
> -----------------------------------------------
>
> Key: CASSANDRA-15241
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15241
> Project: Cassandra
> Issue Type: New Feature
> Components: Feature/Virtual Tables
> Reporter: Chris Lohfink
> Assignee: Chris Lohfink
> Priority: Normal
>
> Expose current running queries and their duration.
> {code}cqlsh> select * from system_views.queries;
> thread_id | duration_micros | task
> ------------------------------+-----------------+---------------------------------------------------------------------------------
> Native-Transport-Requests-17 | 6325 | QUERY
> select * from system_views.queries; [pageSize = 100]
> Native-Transport-Requests-4 | 14681 | EXECUTE
> f4115f91190d4acf09e452637f1f2444 with 0 values at consistency LOCAL_ONE
> Native-Transport-Requests-6 | 14678 | EXECUTE
> f4115f91190d4acf09e452637f1f2444 with 0 values at consistency LOCAL_ONE
> ReadStage-10 | 16535 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-13 | 16535 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-14 | 16535 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-19 | 11861 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-20 | 11861 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-22 | 7279 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-23 | 4716 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-5 | 16535 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-7 | 16535 |
> SELECT * FROM basic.wide1 LIMIT 5000
> ReadStage-8 | 16535 |
> SELECT * FROM basic.wide1 LIMIT 5000{code}
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